size(200);
import graph;
path p=(16,-50)..controls(22.228521478,-45.2480057463)and(27.6338648344,-39.5048284301)..(32,-33)
..controls(36.5190721133,-26.2673204915)and(39.8582744456,-18.820130834)..(42,-11)
..controls(44.696601997,-1.15383629342)and(45.4484954906,9.11644598966)..(48,19)
..controls(50.2663900099,27.7791293293)and(54.1997266664,36.4332033624)..(62,41)
..controls(65.128177681,42.8314424001)and(68.8957515614,43.7597178349)..(72,42)
..controls(75.1215928396,40.2304500745)and(76.17267366,36.5104863049)..(77,33)
..controls(78.8918621163,24.9725074272)and(80.7207923838,16.926747187)..(83,9)
..controls(86.3995717371,-2.82320799244)and(90.8008726313,-14.3691093744)..(97,-25)
..controls(101.150332346,-32.1174096949)and(107.093061599,-38.8754529949)..(115,-38)
..controls(123.063391453,-37.1072245871)and(127.325610477,-28.9575864661)..(130,-21)
..controls(132.55331992,-13.4026534406)and(134.620246366,-5.65309540372)..(137,2)
..controls(142.168459114,18.6213469038)and(148.847528327,34.8465604108)..(159,49)
  ..controls(166.896312468,60.0081549692)and(176.721640935,69.4946790059)..(188,77);
draw(p,linewidth(1));
real l=length(p);
pair P=point(p,0);
pair Q=point(p,l);
pair R=point(p,0.3l);
draw(P--(P.x,0),dashed);
draw(Q--(Q.x,0),dashed);
label("$a$",P.x,N);
label("$b$",Q.x,NW);
label("$\xi$",R.x,S);
label("$O$",(0,0),SW);
xlimits(-10,Q.x+20);
axes("$x$","$y$",Arrow());
